A heavy snow watch is in place for most of the South Island as an "intense cold outbreak" bears down on the country.
MetService late this morning issued the watch from 11pm tomorrow until noon on Thursday. It extends from Marlborough south of the Clarence River to include Canterbury, Otago, Southland and Fiordland.
The forecaster says snow amounts could approach warning criteria above 400 metres.
The polar blast will put the recent balmy spring weather on hold again and is set to bring temperatures as low as -3degC to the southern region over the next two days.
MetService meteorologist Ciaran Doolin said an intense cold outbreak was expected to affect the region tomorrow and Wednesday.
In the Dunedin region, tomorrow would start with possible morning frosts, but as the northerlies changed southwesterly, showers would develop and turn to snow in the evening.
The snow was expected to lower to about 400m in the Dunedin and Southland areas, and 300m in inland Otago.
On Wednesday, brisk southwesterlies would develop in the morning, bringing showers in the afternoon which may again fall as snow, this time possibly to sea level in Dunedin, 300m in Otago and 200m in Southland.
The weather was expected to clear on Thursday.
Mr Doolin said it was a "significant weather event" for October and urged farmers to be prepared for the polar blast which may bring stress to livestock.
"The higher up you are, the more likely it is that you’re going to experience more significant snowfall.
"With this particular event, you’ve got the risk of snow potentially to sea level and in some places you’ve got very cold temperatures, and for a time there will be very strong south-to-southwesterly winds.
"So these are risk factors for stock. Also be aware that unseasonable frosts may affect crops in many areas."
He said driving conditions would also be affected by snow and urged people to proceed with care and keep up to date with the latest MetService forecasts and advice from Waka Kotahi NZ Transport Agency before setting off on journeys.
Alpine roads
MetService says snow is forecast for some alpine roads on Tuesday and Wednesday.
Milford Road (State Highway 94)
From 6pm to 10pm on Tuesday: Snow may affect higher parts of the road for a time in the evening, and up to 1cm of snow may settle on the road above 700 metres. Snow showers may affect the road south of Lake Gunn to near sea level for a time on Wednesday, and this warning may be extended.
Crown Range Road (linking Queenstown and Wanaka)
From 8pm on Tuesday until 2am Wednesday: Snow is forecast to affect the road for a time overnight Tuesday, with 1 or 2cm possibly settling on the road above 600 metres, and lesser amounts down to lower levels. Snow flurries are possible to low-levels during Wednesday afternoon, but little if any snow is expected to settle on the road.
Lindis Pass (SH8)
From 9pm on Tuesday until 3am on Wednesday: Snow is forecast to affect the road for a time overnight Tuesday, with 1 or 2cm possibly settling on the road above 700 metres, and lesser amounts down to 400 metres. Snow flurries are possible to low-levels during Wednesday afternoon, but little if any snow is expected to settle on the road.
Arthur's Pass (SH73)
From 2am until 6am on Wednesday: A brief period of snow is possible in the early hours of Wednesday morning, and 1 to 3cm of snow may settle on the road during this time.
Porters Pass (SH73)
From 3am until 7am on Wednesday: A brief burst of heavy snow is possible in the early hours of Wednesday morning, and 3 to 6cm of snow may settle on the road during this time.
